While a semiconductor wafer having a plurality of integrated circuits formed on its surface is divided into individual semiconductor chips by using a dicing device, etc. and usually they are individually packaged for use on various kinds of electronic devices, there have recently been developed techniques for packaging a plurality of semiconductor chips of the same kind one upon another to form a package improved in storage capacity and processing power or for packaging a plurality of semiconductor chips having different functions to form a package improved in function. And according to those techniques, semiconductor chips are mounted on boards called interposers and the interposers are mounted on a mounting board such as a printed-circuit board, so that the interposers may be interposed between the semiconductor chips and the mounting board.
Each interposer has terminals formed on its upper and lower surfaces and connected to each other by internal wiring. Each terminal on its lower surface has a ball electrode formed thereon, and while each terminal on its upper surface is connected to a bump formed on the lower surface of the semiconductor chip, the ball electrode formed on each terminal on the lower surface of the interposer is connected to an electrode (land) on the mounting board, so that the mounting board and the semiconductor chips may be electrically connected to each other. The use of such interposers makes it possible to realize a reduction in size and weight for various kinds of electronic devices.
When preparing interposers, it is necessary to make flat and uniform the heads of the terminals on the upper and lower surfaces of each interposer in order to ensure reliable connection between the terminals on its upper surface and the bumps formed on semiconductor chips or between the ball electrodes formed on its lower surface and the electrodes on the mounting board. Accordingly, there has been proposed a method employing a grinder for grinding the terminals (see, for example, JP-A-2002-203922, page 7, FIG. 11).
There has also been disclosed a method employing a cutting blade when exposing and making flat and uniform the bumps formed on the lower surface of a CSP instead of the terminals on interposers (see, for example, JP-A-2000-173954, pages 3 to 4).
Every two adjoining terminals formed on any interposer, however, unlike the bump formed on the lower surface of a CSP, have therebetween a distance of only several tens of microns which is too short to be recognized with the naked eye, and any attempt to employ a grinder for grinding the terminals and making their heads uniform in height presents the problem of the terminals being short-circuited due to the ductility of the metal forming the terminals.
Making the heads of the terminals uniform by CMP (chemical mechanical polishing) is a time-consuming job of low productivity and also presents a problem of costly disposal of liquid waste.
These problems are not limited to interposers, but are common to any terminal board having terminals formed thereon in very close proximity to one another. Therefore, it is one object of the invention to make the heads of terminals uniform in height efficiently and economically without having the terminals short-circuited in preparation of a terminal board.